Currently, association of oral diseases such as dental caries and periodontal diseases with the general health is drawing attention. Thus, as therapeutic methods for oral diseases such as dental caries and periodontal diseases, various peptides that exert antimicrobial activity against these causal microorganisms have been developed. For example, Non Patent Literature 1 describes ramnosin A, which is a low-molecular-weight bacteriocin produced by the Lactobacillus rhamnosus 68 strain.
Further, separation and identification of novel lactic acid bacteria that exert antimicrobial activity against causal microorganisms of oral diseases such as cariogenic bacteria and periodontal disease bacteria have been intensively carried out in recent years. For example, the present inventor previously proposed novel lactic acid bacterial strains, the Lactobacillus rhamnosus KO3 strain (L8020 bacterium), the Lactobacillus casei YU3 stain and the Lactobacillus paracasei YU4 strain, which are capable of producing a fermentation product having a wide antimicrobial spectrum against causal microorganisms of oral diseases and having excellent flavor and palatability (see Patent Literature 1). In addition, as therapeutic methods for oral diseases other than techniques of antimicrobial peptides and isolated lactic acid bacterial strains, therapeutic methods using antibiotics have been proposed.